Abstract

The cheese industry has long used a characteristic aspartic proteinase, chymosin (calf rennin) obtained from the calf stomach, as a milk coagulant for cheese making. A severe shortage of chymosin in 1950 stimulated efforts to find substituting microbial enzymes and Arima et al. succeeded in discovering such an enzyme from a fungal strain, Mucor pusillus.1 A similar enzyme was subsequently found from a closely related species, Mucor miehei,2 and these fungal aspartic proteinases are called Mucor rennin. Currently more than a half of cheese in the world is produced with Mucor rennin.